//给定一个二叉树，找出其最大深度。 
//
// 二叉树的深度为根节点到最远叶子节点的最长路径上的节点数。 
//
// 说明: 叶子节点是指没有子节点的节点。 
//
// 示例： 
//给定二叉树 [3,9,20,null,null,15,7]， 
//
//     3
//   / \
//  9  20
//    /  \
//   15   7 
//
// 返回它的最大深度 3 。 
// Related Topics 树 深度优先搜索 递归 
// 👍 778 👎 0

package leetcode.editor.cn;
//Java：二叉树的最大深度
public class MaximumDepthOfBinaryTree{
    public static void main(String[] args) {
        Solution solution = new MaximumDepthOfBinaryTree().new Solution();
        
    }
    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode() {}
        TreeNode(int val) { this.val = val; }
        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }
    //leetcode submit region begin(Prohibit modification and deletion)
/**
    Definition for a binary tree node.
    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode() {}
        TreeNode(int val) { this.val = val; }
        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }
 */
class Solution {
    public int maxDepth(TreeNode root) {
        if ( root == null ){
            return 0;
        }
        else {
            int leftDepth = maxDepth( root.left );
            int rightDepth = maxDepth( root.right );
            //后序遍历
            return Math.max( leftDepth, rightDepth ) +1;
        }
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}
